Autophagy

Autophagy (literally 'self-eating') is a housekeeping process in which cells break down and recycle their own damaged or unneeded components. It is a normal, continuous part of cellular maintenance.

It matters because it is central to cellular quality control and has been linked, largely in animal studies, to healthy ageing. It is often invoked in discussions of fasting, though the human evidence for deliberately maximising it is still preliminary.

In practice, claims that specific fasting protocols reliably 'switch on' beneficial autophagy in humans run ahead of the evidence and should be treated cautiously.